2,449 research outputs found

    A quantum central limit theorem for non-equilibrium systems: Exact local relaxation of correlated states

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    We prove that quantum many-body systems on a one-dimensional lattice locally relax to Gaussian states under non-equilibrium dynamics generated by a bosonic quadratic Hamiltonian. This is true for a large class of initial states - pure or mixed - which have to satisfy merely weak conditions concerning the decay of correlations. The considered setting is a proven instance of a situation where dynamically evolving closed quantum systems locally appear as if they had truly relaxed, to maximum entropy states for fixed second moments. This furthers the understanding of relaxation in suddenly quenched quantum many-body systems. The proof features a non-commutative central limit theorem for non-i.i.d. random variables, showing convergence to Gaussian characteristic functions, giving rise to trace-norm closeness. We briefly relate our findings to ideas of typicality and concentration of measure.Comment: 27 pages, final versio

    Taking reasonable pluralism seriously: an internal critique of political liberalism

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    The later Rawls attempts to offer a non-comprehensive, but nonetheless moral justification in political philosophy. Many critics of political liberalism doubt that this is successful, but Rawlsians often complain that such criticisms rely on the unwarranted assumption that one cannot offer a moral justification other than by taking a philosophically comprehensive route. In this article, I internally criticize the justification strategy employed by the later Rawls. I show that he cannot offer us good grounds for the rational hope that citizens will assign political values priority over non-political values in cases of conflict about political matters. I also suggest an alternative approach to justification in political philosophy (that is, a weak realist, Williams-inspired account) that better respects the later Rawls’s concern with non-comprehensiveness and pluralism than either his own view or more comprehensive approaches. Thus, if we take reasonable pluralism seriously, then we should adopt what Shklar aptly called ‘liberalism of fear’. </jats:p

    Legal Facts and Reasons for Action: Between Deflationary and Robust Conceptions of Law’s Reason-Giving Capacity

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    This chapter considers whether legal requirements can constitute reasons for action independently of the merits of the requirement at hand. While jurisprudential opinion on this question is far from uniform, sceptical views are becoming increasingly dominant. Such views typically contend that, while the law can be indicative of pre-existing reasons, or can trigger pre-existing reasons into operation, it cannot constitute new reasons. This chapter offers support to a somewhat less sceptical position, according to which the fact that a legal requirement has been issued can be a reason for action, yet one that is underpinned by bedrock values which law is apt to serve. Notions discussed here include a value-based conception of reasons as facts ; a distinction between complete and incomplete reasons ; and David Enoch’s idea of triggering reason-giving. Following a discussion of criticism against the view adopted here, the chapter concludes by considering some more ‘robust’ conceptions of law’s reason-giving capacity

    On the NP-Hardness of Approximating Ordering Constraint Satisfaction Problems

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    We show improved NP-hardness of approximating Ordering Constraint Satisfaction Problems (OCSPs). For the two most well-studied OCSPs, Maximum Acyclic Subgraph and Maximum Betweenness, we prove inapproximability of 14/15+ϵ14/15+\epsilon and 1/2+ϵ1/2+\epsilon. An OCSP is said to be approximation resistant if it is hard to approximate better than taking a uniformly random ordering. We prove that the Maximum Non-Betweenness Problem is approximation resistant and that there are width-mm approximation-resistant OCSPs accepting only a fraction 1/(m/2)!1 / (m/2)! of assignments. These results provide the first examples of approximation-resistant OCSPs subject only to P \neq \NP

    Disaggregating political authority: what's wrong with Rawlsian civil disobedience?

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    Contemporary philosophical and theoretical discussions of civil disobedience hope to contribute to significant political debates around when and in which forms political dissent, protest and resistance is appropriate. In doing so, they often focus on and criticize John Rawls' work on civil disobedience. However, ignoring the frame in which Rawls discusses civil disobedience has led critics to wrongly attack his theory for being too restrictive when it is more likely to be too permissive. That permissiveness depends on treating any political order which does not come close to fulfilling his theory of justice as absolutely illegitimate. In this sense, Rawls’ theory of political authority is binary and demanding. The problems his theory shares with most others, including his critics’, show that political authority needs to be disaggregated to make sense of the conditions under which different forms of protest and resistance are appropriate

    Practice-Focused, Constructivist Grounded Theory Methodology In Higher Education Leadership Research

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    A growing body of education research considers practices, however there is less focus on a methodology that enables practical analysis of practices. Use of practice theory is growing, particularly in work and organisational studies, but practice focused studies more frequently address theoretical than methodological agenda. This chapter proposes a practice-focused, constructivist grounded theory methodology as one approach which can address this gap. After first considering the ways in which, separately and in combination, practice-theory and constructivist grounded theory can support higher education leadership and management research, the chapter considers implementation of this methodology by drawing on a study into the practice of authority in higher education leadership. It concludes by considering some implications for the ways in which practices can be understood and the affordances and limitations of this methodology.Peer reviewe

    Impossibility of independence amplification in Kolmogorov complexity theory

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    The paper studies randomness extraction from sources with bounded independence and the issue of independence amplification of sources, using the framework of Kolmogorov complexity. The dependency of strings xx and yy is dep(x,y)=max{C(x)C(xy),C(y)C(yx)}{\rm dep}(x,y) = \max\{C(x) - C(x \mid y), C(y) - C(y\mid x)\}, where C()C(\cdot) denotes the Kolmogorov complexity. It is shown that there exists a computable Kolmogorov extractor ff such that, for any two nn-bit strings with complexity s(n)s(n) and dependency α(n)\alpha(n), it outputs a string of length s(n)s(n) with complexity s(n)α(n)s(n)- \alpha(n) conditioned by any one of the input strings. It is proven that the above are the optimal parameters a Kolmogorov extractor can achieve. It is shown that independence amplification cannot be effectively realized. Specifically, if (after excluding a trivial case) there exist computable functions f1f_1 and f2f_2 such that dep(f1(x,y),f2(x,y))β(n){\rm dep}(f_1(x,y), f_2(x,y)) \leq \beta(n) for all nn-bit strings xx and yy with dep(x,y)α(n){\rm dep}(x,y) \leq \alpha(n), then β(n)α(n)O(logn)\beta(n) \geq \alpha(n) - O(\log n)
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